Method and apparatus for network imposed packet data flow control

ABSTRACT

A method and apparatus provide network-based flow control for mobile station having data connections to the network. In an exemplary embodiment, a Packet Control Function (PCF) in a Radio Access Network (RAN) requests that a Packet Data Serving Node (PDSN) in a Packet Core Network (PCN) turn flow control on and off as needed for mobile station data connections. That is, if the PCF receives data from the PDSN for delivery to a mobile station that the PCF determines to be unavailable, the PCF requests that data transfers from the PDSN be suspended for that mobile station. Such suspension avoids needless continued transfer of undeliverable data to the PCF. The PCF monitors or otherwise determines whether a flow-controlled mobile station has become available again and, if so, notifies the PDSN so that it can lift the suspension and resume data transfers as needed.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/814,550, filed Mar. 31, 2004 and issued on Sep. 8, 2009 as U.S. Pat.No. 7,586,847.

BACKGROUND OF THE INVENTION

The present invention generally relates to wireless communicationnetworks, and particularly relates to packet data flow control withinthe network.

A typical wireless communication network that supports packet dataconnections includes some type of packet network that interfaces mobilestations supported by a radio access network with one or more packetdata networks, such as the Internet. Details vary depending on theequipment vendor and the relevant communication network standards (e.g.,cdma2000, W-CDMA, etc.), but a basic scheme depends on the use of apacket router that routes packet data to and from the radio accessnetwork. In cdma2000 network standards, this packet router is referredto as a Packet Data Serving Node (PDSN).

In turn, the radio access network includes a radio-to-packet interfaceentity that transfers packet data incoming from the PDSN to anassociated Base Station (BS) that provides radio links to one or moremobile stations. The interface entity further transfers packet dataincoming from the mobile stations (via the BS) to the PDSN. In cdma2000network standards, the interface entity is referred to as a PacketControl Function (PCF).

The first time a mobile station connects to the PDSN it establishes apacket data connection with it. Once the mobile station has made thisconnection to the PDSN, the mobile station remains logically connectedto it—subject to time-outs and other resource controls—even though usertraffic links between the PCF and BS and radio links to the mobilestation may be set up and torn down as needed to support the mobilestation's data activity. Processing efficiency and improved packet dataservice is gained by retaining the mobile station's packet dataconnection within the network even when none of the more “precious”radio link resources are allocated to the mobile station.

With the above connection scheme, the PDSN transfers incoming packetdata for a given mobile station to the PCF on the corresponding dataconnection(s) maintained between the PDSN and the PCF. The PCF isresponsible for managing the packet-data “states” of the data-connectedmobile stations by tracking whether each mobile station is “active” or“dormant.” Here, the term dormant broadly connotes a mobile stationhaving no allocated radio links and no allocated PCF-to-BS links tosupport packet data transfer, although radio links still can beallocated for other services, such as voice calls

Because the typical PDSN or like entity has no knowledge regarding theactual availability of its logically connected mobile stations, itsimply transfers incoming packet data to the PCF for delivery to theindividually targeted mobile stations. The PCF is left to determinewhether a targeted mobile station is active or dormant and, if dormant,to undertake operations to establish radio links to it for delivery ofthe data. Buffering the transferred data while waiting for the radioconnection thus represents a key PCF function.

If a radio connection cannot be established for the mobile station, thePCF is unable to deliver the data transferred to it from the PDSN.However, because the PDSN is unaware of the radio connection status or,in general, the availability of the mobile station, that failure oftendoes not prevent the PDSN from continuing its transfer of data to thePCF for delivery to the unavailable mobile station. Such repeatedtransfers can lead to network inefficiencies by requiring the PCF torepeat its buffering and delivery attempt operations for a mobilestation that is at least temporarily unavailable. Further, such faileddelivery attempts can lead to billing/accounting errors in terms ofunrecognized data delivery failures.

SUMMARY OF THE INVENTION

The present invention comprises a method and apparatus to support dataconnection flow control between a Packet Core Network (PCN) and a RadioAccess Network (RAN). An exemplary flow control method comprisesreceiving packet data at the RAN for delivery to a mobile station havingan established data connection with the wireless communication network,determining that the mobile station presently is unavailable fordelivery of the data, and requesting that flow control be turned on forthe mobile station by sending a first flow control message from the RANto the PCN requesting that the PCN stop sending packet data to the RANfor the mobile station. That action stops the PCN from futilelycontinuing to transfer undeliverable data to the RAN and fromsubsequently transferring any new incoming packet data for as long asflow control is turned on for the mobile station.

However, the PCN may retain the mobile station's data connection(s) evenafter turning on flow control. Thus, an exemplary method furthercomprises, if the mobile station becomes available again before the PCNdrops its data connection(s), sending a second flow control message fromthe RAN to the PCN indicating that the PCN may resume sending packetdata as needed to the RAN for the mobile station. Therefore, the presentinvention provides a method of selectively marking or otherwise flaggingdata connections at the PCN that are associated with mobile stationsthat, for one or more reasons, at least temporarily are unavailable fordelivery of packet data from the PCN and unmarking those connectionsafter the mobile stations return to availability. One or more entitiesin the RAN may maintain similar flags for identifying flow-controlledmobile stations.

Thus, in one embodiment, the present invention comprises a flow controlmethod for use in a wireless communication network wherein a Packet CoreNetwork (PCN) supports data connections with one or more mobilestations, and wherein the packet core network transfers data as neededto a Radio Access Network (RAN) for delivery to individual ones of themobile stations. In this context, the method comprises receiving a flowcontrol on message at the PCN from the RAN indicating that flow controlshould be turned on for a mobile station, turning flow control on fordata connections associated with the mobile station and therebysuspending packet data transfers from the PCN to the RAN on those dataconnections. The method further comprises receiving a flow control offmessage at the PCN from the RAN indicating that flow control should beturned off for the mobile station, and turning flow control off for thedata connections associated with the mobile station, thereby resumingpacket data transfers as needed from the PCN to the RAN on those dataconnections.

An exemplary wireless communication system comprises a PCN and a RAN,wherein the PCN includes a Packet Data Serving Node (PDSN) and the RANincludes a Packet Control Function (PCF), which may be associated withor integrated in a Base Station (BS) also included in the RAN. The PCFroutes packets between mobile stations supported by the RAN and thePDSN, and may provide packet-buffering functions for data to bedelivered to the mobile stations. In turn, the PDSN provides packetrouting to the PCF, and may provide gateway routing to external packetnetworks, such as the Internet, in addition to offering other network orvendor specific features.

In an exemplary embodiment of the present invention, the PCF sendsmessages as needed to the PDSN requesting that the PDSN turn on (or turnoff) flow control for established data connections based on whether agiven mobile station is or is not available for delivery of data fromthe PDSN. Thus, the PCF may request that flow control be turned on for agiven mobile station responsive to receiving data from the PDSN for thatmobile station and determining that the data cannot currently bedelivered to the mobile station. In turn, responsive to determining thatthe mobile station has become available again, the PCF may request thatthe PDSN turn off the previously invoked flow control for that mobilestation's data connection(s).

In an exemplary embodiment wherein the network operates according toIS-2001 Inter-Operability standards, the PCF sends “flow control on”messages as A11-Registration Request messages that include a flowcontrol indication, e.g., a Normal Vendor Specific Extension (NVSE)value included in the message that serves as a data off indicator.Further, the PCF sends “flow control off” messages as A11-RegistrationRequest messages that do not include the flow control indication. Inother words, the exemplary PDSN is configured to recognize the absenceof the flow control indication in an A11-Registration Request messagefor a flow-controlled mobile station as an implicit signal to turn flowcontrol off for that mobile station.

Further, the PCF may be supplied with data from the PDSN, for example,indicating which ones of data connections being supported by itcorrespond to “always on” mobile stations, and generate flow controlmessages (flow control on, flow control off) as needed for just thoseconnections. But more broadly, the PCF may generate flow controlmessages for flow controlling any data connection corresponding to amobile station that is not available to receive that data. For example,the PCF may request that the BS attempt to set up a traffic channel forthe mobile station and determine whether radio service for the mobilestation is established responsive to that request. More generally, thePCF may determine whether a mobile station is unavailable for deliveryby cooperating with one or more other entities in the RAN.

For example, the PCF may receive indications of mobile stationavailability from the BS based on signaling from a Mobile SwitchingCenter (MSC). In one embodiment, the MSC is configured to sendnotifications to the BS regarding mobile station registration events,which serve as indications of availability. The MSC can be configured tosend registration notifications for any mobile station that has adormant packet data connection. Further, the MSC can be configured toinfer that flow control has been invoked for any mobile station thatfails to respond to attempted packet data re-activation. As such, theMSC can store logic flags or other flow control indicators and sendreturn-to-availability notifications to the BS specifically forflow-controlled mobile stations. More generally, the MSC can beconfigured to send notifications of registration events for all mobilestations irrespective of whether or not they are flow-controlled.Broadly, the MSC, BS, and PCF all can be configured as needed toimplement the rule that flow control should be turned off where themobile station registers with the network or originates a call.

Rather than passively waiting on such notifications to be receivedthrough the BS, the PCF can actively monitor for a mobile station'sreturn to availability and thereby potentially shorten the time thatflow control is turned on for that mobile station. For example, onceflow control is turned on for a mobile station, the PCF can cause thenetwork to actively “ping” the mobile station by sending a servicerequest for the mobile station to the BS, requesting the BS to setup atraffic channel for the mobile station. In turn, that request, sent asan A9-BS Service Request, causes the BS and associated MSC to page themobile station. If the mobile station timely responds, the PCF receivesan A9-BS Service Response message from the BS, or like messageindicating a successful paging response.

An alternative method for the PCF to “ping” the mobile station is thatthe PCF sends a short data burst to the BS. The short data burst is sentfrom the PCF via an A9-Short Data Delivery message to the BS, whichcauses the BS to send a short data burst to the mobile station directly,or indirectly with cooperation from an associated MSC. If the mobilestation timely responds, the PCF receives an A9-Short Data Ack or likemessage indicating a successful short data burst delivery to the mobilestation, thus its return to availability. The PCF may maintain aninterval timer or other periodic control to periodically initiate are-paging or sending of short data bursts to a flow-controlled mobilestation. Thus, the present invention provides both passive and activemechanisms for turning off flow control once it has been turned on for agiven mobile station.

Those skilled in the art will recognize other features and advantages ofthe present invention upon reading the following description, and uponviewing the associated figures. Of course, the following details shouldnot be construed as limiting the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an exemplary wireless communication network inwhich the present invention may be embodied.

FIG. 2 is an exemplary diagram of data and related connections in thewireless communication network.

FIG. 3 is a diagram of exemplary processing logic for one or moreembodiments of the present invention.

FIG. 4 is a diagram of exemplary processing logic for one or moreembodiments of the present invention.

FIGS. 5A, 5B, 6A, 6B, 7A and 7B are exemplary call timing diagramsillustrating inter-entity messaging supporting one or more embodimentsof exemplary flow control.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described at various points in the belowdiscussion in the context of cdma2000-based networks. However, it shouldbe understood that the present invention's exemplary flow controls canbe applied in other types of wireless communication networks, such asthose based on Wideband (W-CDMA) standards for example.

Turning to the drawings, FIG. 1 illustrates an exemplary wirelesscommunication network 10, which may be configured as a cdma2000 wirelessnetwork. Network 10 comprises a Packet Core Network (PCN) 12 and a RadioAccess Network (RAN) 14 that support communication between users ofmobile stations 16 and various external networks, such as one or morePublic Data Networks (PDNs, e.g., the Internet) 18 and the PublicSwitched Telephone Network (PSTN) 20. PSTN support is not material withrespect to supporting the present invention, which focuses on packetdata operations.

An exemplary PCN 12 comprises a Packet Data Serving Node (PDSN) 30(including a flow controller 31), an IP network 32, an optional gatewayrouter 34, and one or more supporting entities 36 (authentication,foreign agent, etc.). An exemplary RAN 14 comprises a Packet ControlFunction (PCF) 40 (including flow controller 41), a Base Station (BS)comprising a Base Station Controller (BSC) 42 and associated Radio BaseStations (RBSs) 44.

FIG. 2 provides a basis for discussing exemplary network connections andassociated functions that support mobile station packet datacommunications. The BSC 42 is connected to the MSC 46 in theCircuit-Switched Core Network (CSCN) via an A1/A2/A5 interface, to thePCF 40 via an A8/A9 interface, and to the RBSs 44 via an Abis interface.MSs 16 are connected to the RBSs 44 via the Um interface—i.e., the “airinterface” as defined in this example by the IS-2000 standards. Itshould be noted, however, that the present invention is applicable to avariety of network standards.

The PCF 40 is connected to the PDSN 30 via an A10/A11 interface. Asnoted, PCF 40 provides the RAN-to-PDSN interface known as the RP orA10/A11 interface. (IS-2001 defines the RP interface as two separateinterfaces: the A10 interface, which carries user data—packet data fortargeted MSs 16—and the A11 interface, which carries signaling data forcontrol of the packet data connections.) PCF 40 is responsible formanaging the packet-data states (active, dormant) of data-connected MSs16, relaying packets between the MSs 16 and the PDSN 30, and bufferingdata received from the PDSN 30 as needed for delivery to dormant MSs 16.Of course, PCF 40 may perform other functions but of particular interestwith regard to the present invention, the PCF 40 provides flow controlmessaging to the PDSN 30, which may be used by PDSN 30 temporarily tosuspend packet data transfers to PCF 40 for dormant (unavailable) MSs16.

According to terminology adopted herein, PCF 40 sends “first” flowcontrol messages to turn on flow control for selected mobile stations 16(flow control on=data transfers off), and sends “second” flow controlmessages to turn off flow control as appropriate (flow control off=datatransfers on). These first flow control messages also are referred toherein as “flow control on” messages, and the second flow controlmessages are referred to as “flow control off” messages. It should beunderstood that these flow control messages and the attendant flowcontrol operations of PDSN 30 and PCF 40 are network-based flow controlactions independent of any higher layer flow controls, such as thoseenforced by whatever TCP/IP or other types of applications the mobilestations may be running. It also should be understood that, as isexplained herein, that implicit as well as explicit flow control on/offsignaling may be used.

To better understand flow control operations, exemplary connection setupdetails may be helpful. In an exemplary embodiment, to set up apacket-data call, a point-to-point protocol (PPP) session first must beestablished between PDSN 30 and a mobile station 16. The first time aparticular mobile station 16 connects to PDSN 30, it establishes theconnection via a packet-data call. After establishing a PPP connectionwith the PDSN 30, the mobile station 16 remains connected to network 10(subject to timeouts and various other connection controls). Mobilestation 16 or PDSN 30 may initiate subsequent data transmissions overthe PPP connection.

Therefore, network 10 maintains the data connection for mobile station16 even when the mobile station is not engaged in active packet datacommunications. For example, connection resources may remain allocatedon the A10/A11 interfaces between the PDSN 30 and PCF 40. The retentionof data connections during periods of inactivity by the mobile station16 may be controlled by time-outs, or other call teardown controls. Someor all of the mobile stations 16 may be considered to be “always on”devices, which are intended to remain connected to the network 10 andfor which call teardown should be initiated by the PDSN 30 or the alwayson mobile station 16, rather than by the PCF 40. Even in the generalcase of a connected mobile station, it generally is preferable to deferdata connection teardown operations to the PDSN 30 rather than the PCF40 because the PCF 40 serves as an intermediate entity regarding thesemobile station data connections.

However, because the radio resources at RBSs 44 typically represent a“scarce” system resource, a connected mobile station 16 is allocatedradio links as needed to support its actual packet data communications.Therefore, even though its PDSN/PCF data connections are maintained, theradio links to a connected mobile station 16 may be setup and torn downrepeatedly over a period of time based on whether the mobile station 16is or is not sending or receiving packet data.

It is possible, even likely, that PCF 40 will at some point receive datafrom PDSN 30 for delivery to a dormant mobile station 16, which requiresre-activation for successful delivery of the data to it. More generally,PCF 40 may receive packet data on a data connection targeted to alogically connected mobile station 16 that is unavailable for deliveryof packet data. Such unavailability may arise because the mobile station16 is busy in another service that does not permit concurrent deliveryof packet data (or where the network 10 or mobile station 16 in generaldo not support concurrent services), or may arise because the mobilestation 16 is out of radio coverage, e.g., in a radio shadow. Absent thepresent invention, the attempt by PCF 40 to deliver the data transferredto it by PDSN 30 fails due to the unavailability of mobile station 16but PDSN 30 is not apprised of that unavailability and may repeatedlytry to deliver the same or additional data, leading to potential networkinefficiency and data delivery accounting problems.

To address the aforementioned resource inefficiency and accountingdiscrepancy issues, RAN 14 implements a flow control scheme whereby itprovides PCN 12 with information regarding the unavailability, i.e., nodelivery of packet data is possible because of fading, busy state, etc.,of connected mobile stations. An exemplary embodiment of the presentinvention comprises a simple flow control scheme for always on or othermobile stations 16 that stops (suspends) the transfer of data from thePDSN 30 to the PCF 40 if a mobile station is unreachable or otherwiseunavailable. The method may include procedures whereby the PCF 40initiates (periodic) re-paging of the mobile station 16 to determinewhen it becomes available again, or it may receive such indicationindirectly from the MSC 46 via the BSC 42. However determined, the PCF40 recognizing that a flow-controlled mobile station 16 has again becomeavailable triggers it to notify the PDSN 30 so that PDSN 30 can turnflow control off for the mobile station 16 and thereby resumetransferring packet data to the PCF 40 for the mobile station 16 on anas-needed basis.

An initial step in an exemplary embodiment comprises identifying at thePCF 40 those data connections that are associated with always-ondevices. The PCF 40 may exchange information with PDSN 30 at sessionsetup to accomplish this operation. In particular, as part of the packetdata call setup procedure the PDSN 30 may send an indication regardingthe “always on” status of a mobile station 16 to the PCF 40 via a NVSEvalue in the A11 Session Update message sent to the PCF 40. The PCF 40would then store that information as long as that mobile station's A10data connection exists. The PCF 40 would perform flow control as neededfor all such connections. Additionally, the always-on connection statuscan be indicated in an A11-Registration Reply Message.

More broadly, PCF 40 can apply flow control to any data connection forwhich the associated mobile station becomes unreachable. FIG. 3 stepsthrough exemplary processing logic, which may be implemented ashardware, software, or both, at PCF 40 and particularly at flowcontroller 41. Effectively, FIG. 3 outlines an exemplary method wherebythe PCF 40 invokes flow control, i.e., requests that the PDSN 30 turnflow control on for mobile stations 16 that are deemed unavailable, andclears flow control, i.e., requests that the PDSN 30 turn flow controloff, upon determining that a flow-controlled mobile station 16 hasbecome available again.

Assuming that a data connection exists for a given targeted mobilestation 16, processing begins with PCF 40 monitoring for receipt of datafrom PDSN 30 for delivery to the targeted mobile station 16 (Step 100).If data is received and the mobile station's connection is active (Step102), PCF 40 delivers the data to the mobile station via BSC 42/RBSs 44(Step 104). If, however, no radio links currently are allocated to thetargeted mobile station's data connection, PCF 40 initiates anactivation attempt by requesting a service connection to the associatedBSC 42 and meanwhile buffers the data transferred in from PDSN 30 (Step106). If the mobile station 16 is activated (Step 108), PCF 40 proceedswith the data transfer. If PCF 40 determines that the mobile station 16is unavailable, e.g., the mobile station 16 is busy or no radio link forpacket data transfers could be established to it, then PCF 40 sends aflow control on message to the PDSN 30 (Step 110) and may discard thebuffered data.

In an exemplary embodiment, the PCF 40 can invoke flow control for theunavailable mobile station 16 by sending an A11-Registration Requestmessage to the PDSN 30 that includes a flow control indication. PCF 40can be configured to include such indication by setting a NVSE value inthe message to indicate that the PDSN 30 should turn flow control on forthe mobile station 16. Thus, sending this first flow control message tothe PDSN 30 provides it with notification that the targeted mobilestation 16 is unavailable for delivery of the packet data.

From the network's perspective, notifying the PDSN 30 as to the mobilestation's unavailability is preferable to the PCF 40 tearing down theA10/A11 data connection for the mobile station 16. That is, PCF 40 actsas an intermediate transport link in the logical end-to-end sessionconnection between mobile stations 16 and the PDSN 30. As such, it isbetter to allow the PDSN 30 to suspend transfers on the connection and,ultimately, make the decision to tear the connection down if warranted.Of course, the present invention does not prohibit teardown of the dataconnections by PCF 40 if desirable.

Regardless, after invoking flow control at PDSN 30 for the unavailablemobile station 16, which thereby suspends subsequent data transfers fromthe PDSN 30 for that mobile station 16, PCF 40 can monitor for themobile station's return to available status (Steps 112 and 114).Monitoring can be passive or active. In the active case, PCF 40 isconfigured to determine whether the flow-controlled mobile station 16has returned to availability by, for example, periodically initiatingpages of the mobile station or sending short data bursts to the mobilestation. In the case of paging, PCF 40 may initiate paging by sendingone or more A9-BS Service Request messages to BSC 42. In the case ofsending short data bursts, PCF 40 may initiate the bursts by sending oneor more A9-Short Data Delivery messages to BSC 42.

In the passive case, PCF 40 is configured to wait for an indication fromBSC 42 as to when a flow controlled mobile station 16 has returned toavailability. This indication can be in the form of a registration eventor an origination event. For the former case, MSC 46 provides anindication of the registration event to the BSC 42, which in turnprovides notification to PCF 40.

For an origination event as part of call setup, the BSC 42 sets up abearer path to the PCF 40, which is interpreted by PCF 40 as an implicitnotification that the mobile station 16 is available. That is, fororigination events, whether associated with dormant handoff or with adata transfer to the network 10, BSC 42 initiates setup of an A8connection between it and PCF 40 based on sending an A9-Setup-A8 messageto the PCF 40 responsive to an origination event. PCF 40 can thenforward a corresponding A11-Registration Request message. The absence ofa “data off” NVSE value in that registration message results in the PDSN30 turning off flow control for the associated mobile station 16. Thus,the flow control off indicator is indicated implicitly by the absence ofany flow control on indication in the message.

Note that for a registration event, MSC 46 can send an indication in aLocation Update Accept message to inform BSC 42 that a mobile station 16with a dormant packet data session has registered, and the BSC 42 canthen forward this to the PCF 40, which then sends a correspondingA11-Registration Request message to the PDSN 30 to turn flow control offfor the mobile station 16. In another type of event, packet datare-activation is requested for a busy mobile station 16 undercircumstances where concurrent services are not supported. In suchcases, as part of the call clearing process (clear command) for theservice the mobile station 16 was engaged in, the MSC 46 can send anindication to the BSC 42 that the mobile station 16 has returned toavailability for packet data delivery.

In an exemplary embodiment, MSC 46 can be configured to infer that flowcontrol is invoked for any mobile station 16 that does not (or cannot)respond to an attempt to re-activate its dormant packet dataconnections, e.g., it is busy in circumstances that preclude concurrentservices or it is out of radio coverage. Thus, MSC 46 can be configuredto store logical flags indicating which ones of the mobile stations 16it is supporting are flow controlled, and can be programmed to sendre-registration notification messages to BSC 42 for just those mobilestations 16, or for all mobile stations 16, whether or not they aremarked as flow controlled.

Regardless, if PCF 40 determines that a flow-controlled mobile station16 has become available again, it requests that PDSN 30 turn off flowcontrol for that mobile station by sending a flow control off message toPDSN 30 (Step 116). That flow control message can comprise anotherA11-Registration Request message wherein the flow control indication(e.g., NVSE value) is omitted. That is, PDSN 30 can be configured suchthat receipt of an A11-Registration Request message that does notinclude the flow control indication is interpreted as a request to turnflow control off for the corresponding mobile station 16. Alternatively,it may be desirable in some embodiments to configure the PDSN 30 to lookfor an explicit indication that flow control should be turned off.

FIG. 4 steps through exemplary, complementary PDSN processing logic,which may be implemented as hardware, software, or both, at PDSN 30 andparticularly at flow controller 31. Assuming that a data connectionexists for a given mobile station 16, processing begins with PDSN 30monitoring for receipt of data for delivery to it (Step 130). If packetdata is received for the targeted mobile station 16, the PDSN 30 checkswhether the mobile station's connection is marked as suspended, i.e.,marked as being flow-controlled (Step 132). If so, PDSN 30 does nottransfer the data to PCF 40. Note that this allows the PDSN 30 to avoidaccounting errors that might otherwise arise from lost data associatedwith a failed delivery attempt. Thus, PDSN 30 additionally may signal asending entity and adjust data delivery accounting as needed to reflectnon-delivery of the data (Step 134). Enforcing the flow control alsoavoids the inefficiency incurred in conventional networks wherein thedata would be blindly delivered to the PCF for attempted deliverywithout any awareness of whether the mobile station was or was notavailable.

On the other hand, if flow control is not turned on for the targetedmobile station's connection, PDSN 30 transfers the data to PCF 40 fordelivery to the mobile station 16 (Step 136). Since the attempt todeliver the data just transferred to the PCF 40 could trigger adetermination of unavailability by the PCF 40, PDSN 30 monitors forreceipt of a first flow control message from PCF 40 (Step 138). If nosuch message is received, PDSN 30 continues data transfer as needed(Step 140) and processing continues.

If, however, PDSN 30 does receive a flow control on message from PCF 40,it marks the data connection as suspended and suspends the current datatransfer on that connection (Step 142). Additionally, PDSN 30 adjustsits packet data accounting as needed to account for the non-delivery ofthe just transferred data (Step 144). Once the mobile station'sconnection is marked as flow-controlled, PDSN 30 will not undertakesubsequent data transfers on that connection.

In some network standards, such as IS-2000, the PPP connection (datasession) established for a given mobile station 16 can support multiplepacket data service instances, i.e., the mobile station 16 may beassociated with multiple A10 traffic connections, each supporting adifferent packet data flow over the same PPP connection. According toone or more exemplary embodiments of the present invention, the PDSN 30suspends data transfer on all A10 connections associated with a mobilestation 16 when it invokes flow control for that mobile station 16.

Once the PDSN 30 invokes flow control for a particular mobile station16, it monitors for the subsequent receipt of a second flow controlmessage (flow control off) for that mobile station 16 indicating thatdata transfer attempts are once again permitted for the mobile station16 (Step 146). PCF 40 sends such flow control off messages responsive todetermining that a flow-controlled mobile station has become availableagain. If PDSN 30 receives such a message from PCF 40 for aflow-controlled mobile station, it clears the corresponding markedconnections, i.e., lifts the suspension of data transfer from them, andprocessing continues as needed (Step 150).

FIGS. 5A and 5B illustrate exemplary network signaling performed by thevarious entities in support of one or more exemplary embodiments of thepresent invention. In the diagrammed steps, one sees that data incomingto PDSN 30 is targeted to a mobile station 16 having an established dataconnection with PDSN 30. The connection may be dormant but flow controlhas not been turned on for it. PDSN 30 thus transfers the data to PCF 40for delivery to the targeted mobile station 16. That data transfercauses PCF 40 to send an A9-BS Service Request to its associated basestation (e.g., to BSC 42). In turn, BSC 42 sends a BS Service Request tothe supporting MSC 46, which acknowledges with a return BS ServiceResponse.

BSC 42 sends an A9-BS Service Response to PCF 40 after receiving theresponse from MSC 46, which tells PCF 40 that activation of the targetedmobile station 16 has been initiated. PCF 40 thus starts a timer(T_(NETCONN)) that it uses to determine whether the targeted mobilestation 16 timely responds to the re-activation attempt. A short timelater, MSC 46 issues a paging request to BSC 42 (responsive to theearlier BS Service Request), and BSC 42 pages the targeted mobilestation 16.

If PCF 40 does not receive an indication of successful re-activation ofthe targeted mobile station 16 before expiration of its T_(NETCONN)timer, it deems the mobile station 16 as unavailable and requests thatPDSN 30 invoke flow control for the mobile station 16 by sending a firstflow control message in the form of an A11-Registration Request thatindicates data flow at least temporarily should be turned off for themobile station 16. As noted, the flow control message can comprise anA11-Registration Request message that includes a NVSE indicator or othervalue indicating that PDSN 30 should turn flow control on for thetargeted mobile station 16.

Note, too, MSC 46 may set a flow control flag for the targeted mobilestation 16 based on its failure to respond. This function is used inthose embodiments where MSC 46 is configured to specifically notify BSC42 regarding re-registrations received from flow-controlled mobilestations 16. That is, the MSC 46 can use the stored flag to laterdetermine whether it should signal BSC 42 regarding a detected return toavailability by the corresponding mobile station 16.

At roughly the same time, assuming that PCF 40 is configured to activelymonitor for a return to availability of a flow-controlled mobile station16, PCF 40 initiates an inactivity timer (T_(INACTIVE)) that it uses totime the intervals between which it repeats its activation attempts.Thus, upon expiration of its T_(INACTIVE) timer, PCF 40 sends anotherA9-BS Service Request to BSC 42, which initiates another round ofBSC-to-MSC service requests and, ultimately, results in a second attemptto page the targeted mobile station 16. Note that if the initial A9-BSService Response returned by BSC 42 contained an indication that thetargeted mobile station 16 was busy in another service, i.e., busy in aservice that precludes delivery of packet data, then PCF 40 would notrun its T_(NETCONN) timer but rather would immediately start itsT_(INACTIVE) timer to time its subsequent paging attempt.

In the diagram, the second paging attempt is successful. MSC 46, if soconfigured, thus clears its flow-controlled status flag for the mobilestation 16, and PCF 40 sends a second flow control message (data on) toPDSN 30 to indicate that flow control should be turned off for thetargeted mobile station 16 based on its return to availability.

In more detail, if a flow-controlled mobile station 16 responds to are-paging attempt, BSC 42 sends an A9-Setup-A8 message to PCF 40 for theresponding mobile station 16. In turn, PCF 40 requests that PDSN 30 turnoff flow control for the mobile station 16 by sending anA11-Registration Request Message without a NVSE flow control value.

In response to receiving the A11-Registration Request Message from PCF40, the PDSN 30 turns flow control off for the mobile station's dataconnection(s) and returns an A11-Registration Reply message to PCF 40.If the PDSN 30 has no data to transfer to PCF 40 for delivery to mobilestation 16, the returned Registration Reply message includes a DAI setequal to zero. With no data to transfer in from the PDSN 30, PCF 40,recognizing that the connection setup request corresponds to its pagingof the mobile station rather than because the mobile station has data tosend, releases the call and its associated resources, e.g., it sends anA9-Release-A8 Complete message to BSC 42.

Upon receiving that message, BSC 42 releases any corresponding radioresources that may have been allocated to the mobile station 16.Conversely, if the PDSN 30 does have data for the mobile station 16, itwill set the DAI indicator to one (DAI=1) in the A11-Registration Replymessage returned to PCF 40 and the PCF 40/BSC 42 proceed with trafficchannel setup and data delivery, e.g., the A8 connection is establishedbetween PCF 40 and BSC 42, and radio links on the air interface areallocated to mobile station 16 as needed.

FIGS. 6A and 6B illustrate yet another embodiment according to thepresent invention. Here, PCF 40 is configured to initiate the sending ofshort data bursts to flow-controlled mobile stations 16. That is, thereturn to availability of flow-controlled mobile stations 16 can bedetected based on the PCF 40 actively monitoring for them by initiatingthe sending of short data burst messages to them. PCF 40 initiates aninactivity timer (T_(INACTIVE)) that it uses to time the intervalsbetween which it repeats these activation attempts for individual onesof flow-controlled mobile stations 16. Thus, upon expiration of itsT_(INACTIVE) timer for a given flow-controlled mobile station 16, PCF 40sends an A9-Short Data Delivery message to BSC 42. The contents/formatof the message can be pre-configured at PCF 40, or dummy values can beused. In turn, upon receipt of the message, the BSC 42 sends an A9 ShortData Ack to the PCF 40. Even though the message may not convey anymeaningful information to the mobile station 16, its message receiptacknowledgment back to the BSC 42 provides a positive indication thatthe mobile station 16 has returned to availability.

Upon receipt of the A9-Short Data Delivery message, the BSC 42 mayattempt direct delivery of the data burst message to the mobile station16. Alternatively, BSC 42 may send a BS Service Request with a shortdata burst indication and the received values to the supporting MSC,which acknowledges with a return BS Service Response. A short time laterMSC 46 issues a short data burst delivery with the values received inthe BS Service Request via an ADDS Page message to the BSC 42(responsive to earlier BS Service Request), and the BSC 42 sends a shortdata burst message to the targeted mobile station 16.

In the diagram, the short data burst delivery is successful, i.e., eventhough the data burst message may not convey any meaningful informationto the mobile station 16, its data burst message receipt acknowledgmentback to the BSC 42 provides a positive indication that the mobilestation 16 has returned to availability. Thus, MSC 46, if so configured,clears its flow-controlled status flag for the mobile station 16, andPCF 40 sends a second flow control message (data on) to PDSN 30 toindicate that flow control should be turned off for the targeted mobilestation 16. In more detail, if a flow-controlled mobile station 16responds to the short data burst, BSC 42 sends an A9-Update-A8 to PCF 40for the responding mobile station 16. In turn, PCF 40 requests that PDSN30 turn off flow control for the mobile station 16 by sending anA1-Registration Request Message without a NVSE flow control value. Inresponse to receiving the A11-Registration Request Message from PCF 40,the PDSN 30 turns flow control off for the mobile station's dataconnection(s) and returns an A11-Registration Reply message to PCF 40.

In another scenario, the mobile station 16 has packet data to send toPDSN 30 at a time between the network's re-paging attempts. In thiscase, the mobile station 16 will send an Origination message with a DataReady to Send indicator set equal to 1 (DRS=1) to indicate that it hasdata to send. Upon receiving this indication and noting that flowcontrol is turned on for the originating mobile station 16, the BSC42/PCF 40 send an A11-Registration Request message to PDSN 30. Becausethe A-11 Registration Request message omits the flow control onindicator, the PDSN 30 recognizes that flow control should be turned offfor the mobile station 16.

Such an implicit notification rule also provides exemplary handling forscenarios arising under the above described mobile station mobilityevents. For example, flow control might be turned on for a given mobilestation 16 while it is in the packet zone service area of a first PCF 40(termed the “source” PCF). If the mobile station 16 then undergoes a“dormant” (packet data) handoff between the source PCF and a “target”PCF, it will attempt a packet data re-registration through the targetPCF.

The target PCF is not aware of the mobile station's flow-controlledstatus and thus sends a normal mobility-triggered A11-RegistrationRequest message, i.e., no flow control on indicator. Assuming that PDSN30 controls both the source and target PCFs, it will thus receive theA11-Registration Request message for the mobile station 16 from thetarget PCF. Recognizing that flow control is turned on for the mobilestation, and realizing that the re-registration request means that themobile station 16 is once again available, PDSN thus turns flow controloff even though the message from the target PCF did not explicitlyindicate that it should take such action. In other words, flow controlmay be cleared at the PDSN 30 for a mobile station 16 that undergoesinter-PCF handoff irrespective of whether the source PCF 40 that invokedthe flow control ever attempts to clear it.

Thus, in the case of intra-PDSN mobile station dormant handoff, whereboth the source and target PCFs are attached to the same PDSN, the PDSNestablishes a new A10 connection with the target PCF, clears flowcontrol for the mobile station 16, and releases the source side (A10)resources. In response, the source PCF removes all bindings/resourceswith the released A10 connection. Further, if the source PCF has beencarrying on active monitoring/flow control management for the mobilestation, it ceases doing so. That is, source PCFs' flow controlmanagement and return-to-availability monitoring functions (paging,short message delivery attempts, etc.), are ended responsive to themobile station's A10 connection being released.

Note that for inter-PDSN dormant handoffs, the source and target PDSNmay not coordinate the dormant handoff, and thus the source PDSN may notrelease the source PCF's A10 connection for the mobile station. In suchcases, the source PCF may continue its active monitoring for the mobilestation, but such monitoring will be timed-out according to PPP and/orA10 connection timeouts (e.g., inactivity timers). Such timeouts orother implicit notifications thus can be used to cover inter-PDSN andother handoff scenarios and, in general, the PDSN flow controller 32 maybe implemented to enforce the rule that anytime an A11-RegistrationRequest Message is received for a given mobile station 16 without a flowcontrol on indication, the PDSN 30 will turn flow control off.

FIGS. 7A and 7B illustrate similar operations to those shown in FIGS. 5Aand 5B but depict another mechanism for detecting a return toavailability by a mobile station for which flow control has beeninvoked. In the illustration, the targeted mobile station does notrespond to the repeated pages initiated by PCF 40, perhaps because ittemporarily is in a radio “shadow.” One should note that the expirationperiod of T_(INACTIVE) may be set as needed or desired to balance theadvantages gained from quickly determining that a flow-controlled mobilestation has returned to availability versus the potential disadvantagesassociated with PCF 40 initiating pages too frequently.

If a mobile station 16 fails to respond to a page because it istemporarily out of coverage, it may move back into a coverage areabefore the next paging attempt and send a registration request. Therequest may be triggered by the periodic re-registration logic of themobile station (i.e., timer-based re-registration), by its movement inthe RAN 14 (i.e., mobility-event based re-registration), etc. In anycase, the registration event is a clear indication of the mobilestation's return to availability and thus may be used by PCF 40 totrigger its sending of a second flow control message to PDSN 30requesting that flow control be turned off for the mobile station, i.e.,that the data flow suspension be lifted from the mobile station's dataconnection(s).

Noting that registration events may be used by the PCF 40 as indicatorsof mobile station availability highlights the larger point that thepresent invention may, as explained earlier herein, take advantage ofvarious network events as triggers for enabling or disabling dataconnection flow control. Broadly, once it is determined that a targetedmobile station 16 is unavailable for delivery of packet data and flowcontrol is enabled for that mobile station, the PCF 40 may monitor for,or receive notification of one or more network events, from which itdetermines that the flow-controlled mobile station 16 has returned toavailability. According to the present invention, the PCF 40 may play anactive or passive role in that determination but once the determinationis made, PCF 40 signals PDSN 30 to lift the data flow suspension for themobile station 16.

Thus, if a flow-controlled mobile station registers with the network 10,MSC 46 can provide BSC 42 with notification of that event and in turnBSC 42 can signal PCF 40. MSC 46 may be configured to store informationindicating which mobile stations are under flow control and sendnotification when any of those mobile stations register (re-register)with network 10. In this case, MSC 46 clears any flow-controlled flag orlike indicator stored by it for such mobile stations 16. Alternatively,rather than provide registration notifications only for mobile stationsspecifically marked as flow-controlled, MSC 46 can be configured to sendregistration notifications to BSC 42 for any mobile station 16 having adormant packet data connection. In that case, either BSC 42 or PCF 40may be configured to sort out whether any such notification correspondsto a mobile station 16 that is under flow control.

Also, as mentioned earlier herein, the MSC 42 can be configured to senda return-to-availability notification at call teardown for a mobilestation 16 wherein an earlier packet data session re-activation failedbecause the mobile station 16 was busy. Thus, when the service thatprecluded re-activation of the mobile station's packet data session isended, MSC 42 sends, as part of the call clearing process, anotification to the BSC 42, which in turn notifies PCF 40. In responseto such notification, PCF 40 requests that PDSN 30 turn flow control offfor the mobile station 16.

Also, as noted earlier, PCF 40 may be configured to actively determineavailability by actively monitoring for the mobile station's return toavailability, such as by pinging—i.e., initiating one or more pages—fora flow-controlled mobile station. With that approach, the PCF 40 canselect a pinging interval, e.g., once per minute, that allows relativelyquick detection of a return to availability without imposing significantpaging overhead on the network 10. T_(INACTIVE) can be a dynamicallyadjusted timer that provides control to the PCF as to when and how toinitiate re-connect attempts. For example T_(INACTIVE)=2*T_(INACTIVE)(double the interval between re-tries each time).

Also, flow control may be applied to unreachable as well as “busy”mobile stations, i.e., a mobile station that is in radio contact but forwhich no additional radio channel(s) can be allocated for delivery ofthe pending packet data. In the busy case, the MSC 46 can inform BSC42/PCF 40 about this state and the PCF 40 can invoke flow controlimmediately upon receipt of an A9-BS Service Response that indicates thebusy condition. Instead, PCF 40 can start T_(INACTIVE) to time asubsequent paging attempt.

Those skilled in the art should appreciate that discussion of thepresent invention in the context of cdma2000 (IS-2000) architectures andnomenclature should not be construed as limiting it to such contexts.While offering significant advantages to cdma2000 networks, the presentinvention more generally offers an apparatus and method allowing a RANto notify a PCN as to the unavailability of mobile stations havingestablished data connections at the PCN. So apprised, the PCN avoids theinefficiencies arising from the transfer of undeliverable packet data.As such, the present invention is not limited by the foregoing detailsand, indeed, is limited only by the following claims and theirreasonable equivalents.

1. A method of flow control in a wireless communication networkcomprising: receiving data for a dormant mobile station at a PacketControl Function (PCF) for delivery to the mobile station; determiningthat the mobile station is unavailable for delivery of the data, whereindetermining that the mobile station is unavailable for delivery of thedata comprises determining whether the dormant mobile station can beactivated for delivery of the data by sending a service request for themobile station to an associated Base Station Controller (BSC) andstarting a connection timer and, if the dormant mobile station has notresponded before expiration of the connection timer, determining thatthe dormant mobile station cannot be re-activated for delivery of thedata; and sending a message to a Packet Data Serving Node (PDSN)requesting it to turn flow control on for the mobile station bysuspending further transfers of data to the PCF for the mobile station;subsequently determining that the mobile station has become availableagain; and in response to the mobile station availability, sending amessage to the PDSN requesting it to turn flow control off for themobile station by resuming transfers of data to the PCF for the mobilestation; wherein the PCF requests the PDSN to suspend or resumetransfers of data to the PCF for the mobile station based on includingor omitting one or more flow control indications in defined registrationmessages generated by the PCF and sent to the PDSN.
 2. The method ofclaim 1, wherein determining that the mobile station has becomeavailable again comprises receiving notification of a registration ororigination event involving the mobile station.
 3. The method of claim1, wherein determining that the mobile station has become availableagain comprises sending a service request for the mobile station fromthe PCF to an associated Base Station Controller (BSC) included in theRAN and determining whether the RAN successfully establishes radioservice for the mobile station.
 4. The method of claim 1, wherein thePCF requests the PDSN to turn flow control on for the mobile station byincluding a data off indicator in a packet data registration messagesent by the PCF to the PDSN for the mobile station.
 5. The method ofclaim 4, wherein the PCF requests the PDSN to turn flow control off forthe mobile station by not including the data off indicator in anotherpacket data registration message sent by the PCF to the PDSN for themobile station.
 6. The method of claim 1, wherein determining whetherthe dormant mobile station can be re-activated for delivery of the datacomprises, if the mobile station is busy such that delivery of packetdata is precluded, starting a reactivation timer at the PCF and, uponexpiration of the reactivation timer, sending a service request for themobile station from the PCF to an associated Base Station Controller(BSC).
 7. The method of claim 1, further comprising starting anactivation timer upon expiration of the connection timer to time asubsequent transmission of a service request from the PCF to the BSCand, if the dormant mobile station does not respond to the subsequentservice request, sending one or more additional service requestsaccording to periodic expirations of the activation timer.
 8. The methodof claim 1, further comprising sending notifications of mobile stationregistration events from a Mobile Switching Center (MSC) of the networkto a Base Station Controller (BSC) associated with the PCF to apprisethe PCF regarding the availability of mobile stations.
 9. The method ofclaim 8, further comprising, at the PCF, sending a message to the PDSNrequesting that it turn off flow control for a particular mobile stationresponsive to receiving a notification of registration for thatparticular mobile station via the BSC.
 10. The method of claim 1,further comprising, at a Mobile Switching Center (MSC), determining thatflow control is turned on for a particular mobile station responsive torecognizing that the mobile station has failed to respond to a pagingattempt initiated by the MSC responsive to an associated Base Station(BS) service request for the mobile station.
 11. The method of claim 10,further comprising storing one or more flow control flags at the MSC toidentify which particular mobile stations supported by the MSC areflow-controlled mobile stations, and further comprising sendingnotifications of mobile station registrations involving anyflow-controlled mobile station to a BSC associated with the PCF so thatthe PCF is apprised whenever any flow-controlled mobile station isinvolved in a registration event.
 12. A Packet Control Function (PCF)for use in a wireless communication that includes a Packet Core Network(PCN) and a Radio Access Network (RAN), the PCF comprising: a packetdata interface circuit configured to support packet data connectionsbetween the RAN and the PCN; and a flow control circuit configured torequest the PCN to suspend and resume data transfers as needed for oneor more mobile station data connections based on the availability ofthose mobile stations for delivery of packet data; wherein, once the PCFrequests the PCN to suspend data transfer for a particular mobilestation, the PCF is configured to initiate one or more paging or shortdata delivery burst attempts for that particular mobile station todetermine whether that particular mobile station has returned toavailability, and wherein the flow control circuit includes anactivation timer and the PCF is configured to initiate one of the pagingattempts or one of the short data delivery attempts at each of one ormore expiration intervals of the activation timer; wherein the PCF isfurther configured to request the PCN to suspend data transfers for aparticular mobile station by requesting that a Packet Data Serving Node(PDSN) at the PCN turn flow control on for that particular mobilestation, and is configured to request the PCN to resume data transfersas needed for a particular mobile station by requesting that the PDSNturn flow control off for that particular mobile station, wherein thePCF requests the PDSN to turn flow control on or off for the mobilestation include or omit one or more flow control indications in definedregistration messages generated by the PCF and sent to the PDSN.
 13. ThePCF of claim 12, wherein the PCF requests the PDSN to turn flow controlon for a particular mobile station by sending a first flow controlmessage and requests the PDSN to turn flow control off for thatparticular mobile station by sending a second flow control message. 14.The PCF of claim 12, wherein the PCF sends the first and second flowcontrol messages to the PDSN as registration request messages butwherein it denotes a given registration request message as a first orsecond flow control message by including or not including, respectively,a data off indicator in the given registration request message.
 15. ThePCF of claim 12, wherein the PCF is configured to receive data from thePCN for delivery to a mobile station having an established dataconnection, and determine whether the mobile station is available fordelivery of the data, and wherein the flow control circuit is configuredto send a message requesting that the PCN suspend transfer of data tothe PCF for the mobile station if the mobile station is unavailable. 16.The PCF of claim 15, wherein the PCF is configured to determine if themobile station becomes available again, and wherein the flow controlcircuit is configured to send a message requesting the PCN to lift thesuspension of data transfer for the mobile station if the mobile stationbecomes available again.
 17. The PCF of claim 12, wherein the PCF isconfigured to determine whether a mobile station is available orunavailable by determining whether a radio link for the delivery ofpacket data can be timely established for the mobile station.
 18. ThePCF of claim 17, wherein the PCF is configured to determine whether amobile station that previously was determined to be unavailable becomesavailable again, and to inform the PCN of that return to availability.